Gluttony

I instantly threw a spear at the doppelganger, in an attempt to stop his ritual.

If Belial was to descend here and now, it will be the worst possible outcome. Screw the butterfly effect, this will cause a chain reaction of the worst and most epic proportions ever. Belial is an entity that's only supposed to appear, not even in the physical form in the second phase.

He still hasn't even gathered enough followers to be able to manifest his power, but how come the system is mention that he's descending?!

As the spear flew toward the doppelganger it pierced right through his heart, stopping his ritual for a second.

I knew that blow wasn't enough to kill it, since I didn't receive any notification, but in that second I was able to see how he was able to start this ritual.

Around the entirety of the hall, more than a dozen sludge-like substance was on the ground.

This purple sludge is something I know, it's a doppelganger's corpse.